1. Field of the Invention
The present invention relates to a system for controlling the efficient operation of a pumped hydrocyclone liquid separating unit and, more particularly, to such a control system which maintains a desired backpressure within the hydrocyclones.
2. Setting of the Invention
Liquid separators, and especially hydrocyclones, are well-known for use in separating different density fractions of liquids, such as oil and water. Hydrocyclones have been utilized extensively within oil production facilities where environmental considerations require that only a minute amount of oil be discharged with separated produced water.
On offshore oil production facilities, there is a need for minimizing the weight and size of onboard equipment. To meet this need, various configurations of hydrocyclone systems have been developed. One configuration that has been found to be desirous is a pumped hydrocyclone liquid separating unit, and generally includes one or more hydrocyclones arranged in parallel flow with the liquid mixture introduced into the hydrocyclones under pressure.
One problem common to utilizing hydrocyclones in any configuration of liquid separating units is that separation efficiency of the hydrocyclones is extremely sensitive to the liquid introduction pressure and rate and the backpressure of the separated liquids exiting the hydrocyclones. Various control devices and piping arrangements have been used to control the flow of liquid through the banks of hydrocyclones and have included the use of preprocessing units to provide a more constant flow of liquid to the pump and liquid level control valves thereon to maintain the desired backpressure. One major problem encountered with this configuration has been that the surges of liquid from the wells entering preprocessing units have caused the backpressure control system to over-compensate resulting in a drastic reduction in backpressure. Thus, the hydrocyclones pass unacceptable quantities of oil to be discharged with the separated water and cause unacceptable vibration.
There is a need for a pumped hydrocyclone backpressure control system which maintains the desired backpressure within the liquid separation unit so that the banks of hydrocyclones are operated within the most efficient volume flow and backpressure parameters.